Paul, I just got my 300 Win built on a defiance action with a 28" Broughton 5C barrel finished. Plus I load for 3 other 300 wins including my sons custom. Here is what they all liked with a 210 Berger.

Lapua 300 win brass.

Fed GM 215 M primer

H-1000 (start at 72 gr and work up) But probably in the 76 to 77 gr area you will see what you want foe velocity and accuracy. I am slightly over this and get 2995 fps from mine. My sons is at 77 gr and gets 2916 fps. neither are showing signs of pressure. But I have seen stock rifles show pressure at 74. This is why I say work it up and waych.

Seating is different with each rifle. I start at .040" off the lands then load a few at .050 and see if it likes it. If it does I keep going looking for the sweet spot. f it didnt like moving them farther off the lands I load some at .030 off lands and try that. Once you have a direction I test in .005 increments.